Heretofore, in flat panel displays such as, typically, liquid crystal displays, a very small electronic device such as a thin film transistor (TFT) is formed in the vicinity of each pixel constituting the face of a display in accordance with the same process as that used for producing semiconductor integrated circuits, in which insulation films, semiconductor films and the like are successively laminated, for example on a glass substrate in accordance with the CVD process (the chemical vapor deposition process), and switching on, switching off and control of the contrasting density of each pixel are conducted using the device. In other words, the very small electronic devices such as TFT are prepared directly on the glass substrate. However, the above technology has problems in that it is inevitable that the cost is increased due to the complicated process having many stages, and that the apparatus for the CVD process for forming the films on the glass substrate becomes great as the area of the display is increased, and the cost is increased markedly.
To overcome the above problems, a technology in which very small integrated circuit chips of crystalline silicon are attached to a printing plate in a manner similar to that used for printing ink, then, transferred to prescribed positions on a glass substrate for displays by a means such as printing technology and fixed there so that the cost can be decreased, is disclosed (refer, for example, to Patent Reference 1). In this technology, a film of a macromolecule is formed on the glass substrate in advance, the very small integrated circuits of crystalline silicon are transferred to the film by printing technology or the like, and the chips are embedded into the film of a macromolecule in accordance with a process such as the heat molding and the heat pressing. However, problems such as deformation of the film and formation of bubbles in the film tend to arise and, moreover, the process is not efficient due to the time required for the heating.
A sheet for circuit boards which enables to embedding circuit chips without heating by using a resin sheet for circuit boards comprising a macromolecular material of the energy curable type in place of the film of a macromolecule described above and controlling the storage moduli of the resin sheet during and after the embedding of the circuit chips, is disclosed (refer, for example, to Patent Reference 2).
A circuit board for displays having embedded circuit chips can be produced efficiently with excellent productivity by using the resin sheet for circuit boards described above. However, the cured products of the resin sheets comprising conventional macromolecular materials of the energy curable type do not always exhibit satisfactory heat resistance, and a problem arises in that cracks are formed in wiring formed on the cured products having embedded circuit chips.    [Patent Reference 1] Japanese Patent Application Laid-Open No. 2003-248436    [Patent Reference 2] Japanese Patent Application Laid-Open No. 2006-323335